There are now 74 confirmed and suspected cases of Legionnaires' disease amid an outbreak in the Scottish capital.

It also emerged that the Health and Safety Executive (HSE) has served an improvement notice on an Edinburgh company for alleged failures to adequately control the risk of Legionella in a cooling tower.

The notice was served on the North British Distillery Company and refers to a tower in Wheatfield Road in Edinburgh.

An HSE statement said the firm has already taken all three of its cooling towers at the site out of operation. Issuing the improvement notice does not mean the tower concerned is where the outbreak originated.

The search for the source of the disease outbreak has centred on cooling towers at four sites in the south-west of the city, which have been "shock-treated" with chemicals.

Scottish Health Secretary Nicola Sturgeon has said it is "not always possible to conclusively determine the precise source of an outbreak".

She said the increase of 13 in the total number of confirmed and suspected cases had been expected.

A micrograph picture of the Legionionella pneumophilia bactera. The bacteria replicates quickly, part of what makes the disease so infectious

Twenty-eight people have now been confirmed as having Legionnaires' disease and another 46 are suspected of having it.

One man has died, named locally as 56-year-old Robert Air from the Seafield area of the city, has died of the illness so far.

Fourteen people are in intensive care, a further 30 are in general hospital wards, 15 are being treated in the community and 10 have already been discharged from hospital.

Ms Sturgeon said: "As we expected, we have seen a rise in the number of cases associated with this outbreak today. It is reassuring to see that 10 people have now been discharged from hospital."

A newly set-up helpline has received dozens of calls already, Sturgeon said.

"I think over the period from 3 o'clock yesterday, when it went live, to this morning there was something in the region of 50 calls made to it. NHS 24 had also been reporting an increase in calls to their general line, which may have been related to Legionella."

Those confirmed as having the disease range in age from 33 to 76, with more men than women infected.

Four patients are now being cared for outside the NHS Lothian area: one in Glasgow, one in the north of England, one in the NHS Tayside area and one in NHS Lanarkshire. All these cases are considered to be linked to the outbreak in the south-west of Edinburgh.